Prior to the present invention, viewers of (so called) three-dimensional (3-D) holograms were required to view the reflected image(s) within the line-of-sight range of a holographic projection plate. If the viewer's eyes were moved out of the narrow range of the reflected images, the image would "disappear". In essence, the viewer's eyes were the "display medium" for the hologrammetric images.
Real time, 3-D image display has been the focus of many development efforts. However, the lack of an ideal display medium and apparatus has been the primary limiting factor for obtaining a practical system. For example, conventional holograms (e.g. dichromated gelatin hologram) are able to display a real or virtual 3-D image with only a limited perspective angle. A 3-D image could also be viewed by projecting polarization-encoded stereo images on a large screen or TV monitor. However, the fact that viewer has to wear polarizing goggles, with a narrow field of view, severely limits its visualization applications. Recently, a 3-D image display technique using a laser scanner and rotation screen has been developed (Texas Instrument). In operation, a scanning laser beam is synchronized with a 3-D rotating diffusive screen to display a time-multiplexed 3-D image. The volume of this displayed image is limited due to the need of spinning a large screen at a high speed.
A search of the prior art has resulted in the following patents of some relevance to the present invention:
4,402,927 von Dardel et al 4,610,863 Tewari et al 4,994,672 Cross et al 5,086,085 Pekala 5,111,313 Shires 5,119,214 Nishii et al 5,242,647 Poco 5,294,480 Mielke et al 5,347,644 Sedlmayr 5,400,155 Ueda et al 5,483,364 Ishimoto et al 5,561,537 Aritake et al 5,570,208 Kato et al 5,594,559 Sato et al 5,644,324 Maguire, Jr. 5,644,414 Kato et al 5,717,509 Kato et al 5,724,162 Garcia et al 5,739,812 Mochizuki et al 5,748,382 Maguire, Jr.
Of the foregoing, the following appear to be of greater relevance:
U.S. Pat. No. 5,347,644 to Sedimayr is directed to a three-dimensional image display device and systems and methods for implementation. The three-dimensional image display device has a projection screen 175 as shown in FIG. 5. The projection screen display device has multiple layers of transparent material each with a unique coating. A beam of collimated white light 50 has the infrared energy removed and the resultant beam 55 is processed as shown in FIG. 4 by splitting the beam, filtering it, and passing it through a liquid crystal device acting as a PEMFVORFD, a programmable electromagnetic wave field orientation rotating device. The coating on the various layers 200, 202, 204 . . . of the display device each is reflective to an electric field vector that has an orientation at a specific angle. With the beam passing through the transparent layers, the selective reflection of the layers provides a solid image for display.
U.S. Pat. No. 5,111,313 to Shires is directed to a real time electronically modulated cylindrical holographic auto stereoscope that can display a three-dimensional image over a 360 degree viewing area without using special glasses, the display being in real time from remotely gathered images. Eight laser diodes 15 each with a collimating lens 16 project a beam 20 through a common cylindrical lens 17 through a slit 18 and onto a cylindrical HOE (hologram optical element) 10. The HOE has eight raster scan tracks 11, each track having thousands of contiguous holograms. The laser beams 20 fall on subsequent HRS holograms as the HOE is rotated with the beam being diffracted at different pre-defined angles. The beam then defines pixels on a holographic direction selective screen 13. As the HOE 10 is spun on its axis of symmetry by motor 14, different holograms on different portions of the corresponding HRS track 11 can be sequentially reconstructed by light beam 20 and illuminated on HDSS holograms 13. A particular sequence of scanning pixels can vary greatly, as long as each horizontal viewing zone is presented with one complete unique raster scan. An audience around the HOE can see any given pixel as it is scanned horizontally, but it produces a vertical line image. Thus, vertical movement on the part of the viewer will not provide a new perspective.
U.S. Pat. No. 5,086,085 to Pekala is directed to processing Aerogels that are transparent, essentially colorless and exhibit continuous porosity and ultra fine cell size. The aqueous sol-gel polymerization of malamine with formaldehyde, followed by super-critical extraction leads to the formation of the new type of organic Aerogel. The formation followed by super-critical drying produces the improved Aerogels. The transparent silica Aerogel formed by this inventive process can be sheets or slabs that have substantially better optical and structural characteristics compared to conventional processing. The process of forming these Aerogels is the same except for an improved super-critical drying process using a solvent such as CO.sub.2. Using this drying process provides higher process yields, reduced processing time and structurally sound Aerogels.
U.S. Pat. No. 5,739,812 to Mochizuki et al is directed to a system for inputting image and commands using a three-dimensional mouse capable of generating in real-time a three-dimensional image. The three-dimensional system has a radiation source 10 with oscillator 11 and dipole antenna 13, with a radiation controlling switch 15. A two-dimensional microstrip antenna unit 16 with a plurality of elements 23 is capable of receiving the electromagnetic wave within the frequency range of 100 MHZ to 50 Ghz so as to select a frequency of the hologram. The size of the antenna array 16 is substantially equal to a size of a three-dimensional object, a space in which the transmitting dipole antenna 23 is moved. The signal from the antenna is sent to the hologram data collecting circuit 17. A holder of the transmitting dipole antenna 13 movable in the three-dimensional directions defines the virtual space which is produced by the system. A command inputting unit 21 held by the hand of the operator inputs signals to the host computer. Host computer 20 responds to these signals as well as the data obtained from the transmitting dipole antenna 13's movement. A stereoscopic unit 22 mounted on the head of the operator displays a point image, a line image and a three-dimensional image, in response to the data from the computer 20.